linux-kernel - Re: [PATCH v2 6/7] x86/entry/64: Remove TRACE_IRQS_*

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Date:   Thu, 11 Jul 2019 10:05:17 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     tglx@...utronix.de, bp@...en8.de, mingo@...nel.org,
        luto@...nel.org, torvalds@...ux-foundation.org, hpa@...or.com,
        dave.hansen@...ux.intel.com, jgross@...e.com,
        linux-kernel@...r.kernel.org, zhe.he@...driver.com,
        joel@...lfernandes.org, devel@...ukata.com
Subject: Re: [PATCH v2 6/7] x86/entry/64: Remove TRACE_IRQS_*_DEBUG

On Wed, Jul 10, 2019 at 11:24:56PM -0400, Steven Rostedt wrote:
> On Thu, 04 Jul 2019 21:56:01 +0200
> Peter Zijlstra <peterz@...radead.org> wrote:
> 
> > Since INT3/#BP no longer runs on an IST, this workaround is no longer
> > required.
> > 
> > Tested by running lockdep+ftrace as described in the initial commit:
> > 
> >   5963e317b1e9 ("ftrace/x86: Do not change stacks in DEBUG when calling lockdep")
> 
> It looks like a clean revert, and it passed my ftrace smoke tests with
> lockdep enabled (although I triggered a locked warning unrelated to
> this, with the text_mutex and module_mutex, but I'm hoping my tree has
> the fixes for that).
> 
> Reviewed-by: Steven Rostedt (VMware) <rostedt@...dmis.org>

Thanks!

> Hmm, does this mean we can remove the IDT switching in the NMI handler
> as well?

I'll have to go look at that; there still are ISTs and NMIs can still
hit those.